2.8. Getting User Input

At this point, you're probably wondering how to get a value
from the keyboard into a Perl program. Here's the simplest way:
use the line-input operator,
<STDIN>.[61] Each time you use <STDIN> in a
place where a scalar value is expected, Perl reads the next complete
text line from standard
input (up to the first newline), and uses that
string as the value of <STDIN>. Standard
input can mean many things, but unless you do something uncommon, it
means the keyboard of the user who invoked your program (probably
you). If there's nothing waiting to be read (typically the
case, unless you type ahead a complete line), the Perl program will
stop and wait for you to enter some characters followed by a newline
(return).[62]

[62]To be honest, it's normally your
system that waits for the input; Perl waits for your system. Although
the details depend upon your system and its configuration, you can
generally correct your mistyping with a backspace key before you
press return -- your system handles that, not Perl itself. If you
need more control over the input, get the
Term::ReadLine module from CPAN.

The string value of <STDIN> typically has a
newline character on the end of it.[63] So you could do something like this:

[63]The exception is
if the standard input stream somehow runs out in the middle of a
line. But that's not a proper text file, of course!